In order to increase the operational speed of LSIs, it is required to decrease the specific dielectric constant of inter-level insulating films. As an inter-level insulating film with a low dielectric constant, an organosiloxane film is known. Where an organosiloxane film is formed, a coating film of a polysiloxane base solution having an organic functional group is first formed by spin coating on a target substrate, such as a semiconductor wafer. Then, a heat process (baking process) is performed on the wafer to bake the coating film.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2001-308089 discloses a method of forming an organosiloxane film of this kind. According to this method, a process of baking a coating film is performed at a temperature of, e.g., from 400 to 450° C. for about 30 minutes. This baking process is performed within a nitrogen atmosphere to prevent organic functional groups from decomposing.
Jpn. Pat. Appln. KOKAI Publication No. 2003-158126 (published on May 30, 2003), discloses an improved method of forming an organosiloxane film. According to this method, a catalytic gas, such as a mixture gas of ammonia and water, dinitrogen oxide gas, or hydrogen gas, is used in the baking process. In this case, the process temperature can be lowered to a temperature of from 300 to 400° C.